Semiconductor device, and method for manufacturing semiconductor device

ABSTRACT

[Object] To provide a semiconductor device capable of improving a discharge starting voltage when measuring electric characteristics, and widening a pad area of a surface electrode or increasing the number of semiconductor devices (number of chips) to be obtained from one wafer, and a method for manufacturing the same.[Solution Means] A semiconductor device 1 includes an n-type SiC layer 2 having a first surface 2A, a second surface 2B, and end faces 2C, a p-type voltage relaxing layer 7 formed in the SiC layer 2 so as to be exposed to the end portion of the first surface 2A of the SiC layer 2, an insulating layer 8 formed on the SiC layer 2 so as to cover the voltage relaxing layer 7, and an anode electrode 9 that is connected to the first surface 2A of the SiC layer 2 through the insulating layer 8 and has a pad area 95 selectively exposed.

TECHNICAL FIELD

The present invention relates to a semiconductor device using SiC and amethod for manufacturing the same.

BACKGROUND ART

Conventionally, a problem of discharge in the atmosphere occurs whenmeasuring electric characteristics of a high withstand voltagesemiconductor device.

As a measure against this, for example, Patent Document 1 discloses amethod for manufacturing a semiconductor device, including steps offorming base regions and emitter regions on a semiconductor wafer,patterning a base electrode and an emitter electrode, and then fittingand patterning a polyimide film onto the surface to cover regions exceptfor a dicing region and other electrode bonding portions.

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Application Publication No. 60-50937

Patent Document 2: Japanese Patent Application Publication No. 54-45570

Patent Document 3: Japanese Patent Application Publication No.2011-243837

Patent Document 4: Japanese Patent Application Publication No.2001-176876

Patent Document 5: Japanese re-publication of PCT internationalapplication No. WO2009/101668

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a semiconductor devicecapable of improving a discharge starting voltage when measuringelectric characteristics, and widening a pad area of a surface electrodeto be larger than conventionally, and a method for manufacturing thesame.

Another object of the present invention is to provide a semiconductordevice capable of improving a discharge starting voltage when measuringelectric characteristics, and increasing the number of semiconductordevices (number of chips) to be obtained from one wafer to be largerthan conventionally, and a method for manufacturing the same.

Means for Solving the Problems

A semiconductor device according to the present invention includes afirst conductive-type SiC layer having a first surface, a second surfaceand end faces surrounding the first surface and the second surface, theSiC layer having a semiconductor device structure, a secondconductive-type voltage relaxing layer formed in the SiC layer such thatthe voltage relaxing layer is exposed to an end portion of the firstsurface of the SiC layer, an insulating layer covering the voltagerelaxing layer, and a surface electrode connected to the first surfaceof the SiC layer through the insulating layer, the surface electrodehaving a pad area selectively exposed (Claim 1).

This semiconductor device can be manufactured by a method formanufacturing a semiconductor device, including the steps of, in a firstconductive-type SiC wafer which has a first surface and a second surfaceand a dicing region with a predetermined width set to segment aplurality of device regions, forming a semiconductor device structure ineach of the device regions, forming a second conductive-type voltagerelaxing layer with a width wider than that of the dicing region alongthe dicing region so as to be across the device regions adjacent to eachother, forming an insulating layer on the SiC wafer so as to cover thevoltage relaxing layer, forming a surface electrode in each of thedevice regions so that the surface electrode is connected to the firstsurface of the SiC wafer through the insulating layer and partiallyselectively exposed as a pad area, measuring electric characteristics ofthe semiconductor device structure of the device regions by applying amaximum applied voltage (BV) that generates a potential difference of1000 V or more between the surface electrode and the SiC wafer in one ofthe device regions, and dividing the SiC wafer into individual pieces ofthe plurality of semiconductor devices by cutting the SiC wafer alongthe dicing region (Claim 20).

When measuring electric characteristics of the semiconductor devicestructure, in order to prevent discharge between the dicing region andthe surface electrode, the discharge starting voltage V between thedicing region and the surface electrode must be set to a value higherthan the maximum applied voltage (BV) (≥1000 V). The maximum appliedvoltage (BV) is a voltage (breakdown voltage: BV) when the semiconductordevice structure causes avalanche breakdown, and between the dicingregion and the surface electrode, a potential difference correspondingto this maximum applied voltage (BV) occurs. On the other hand, thedischarge starting voltage V is a voltage when an insulator such as theatmosphere present between the dicing region and the surface electrodeis broken down and an electric current starts to flow between the dicingregion and the surface electrode. Specifically, as long as therelationship of the discharge starting voltage V>the maximum appliedvoltage (BV) is satisfied, an insulated condition between the dicingregion and the surface electrode is maintained.

Therefore, according to the present invention, a voltage relaxing layeris formed along the dicing region, and further, the voltage relaxinglayer is covered by an insulating layer. Therefore, when measuringelectric characteristics of the semiconductor device structure, themaximum applied voltage (BV) can be relaxed in two stages of theinsulating layer and the voltage relaxing layer. Accordingly, the burdenof the voltage on the atmosphere between the dicing region and thesurface electrode can be eased. In other words, the voltage appliedbetween the dicing region and the surface electrode can be divided bythe atmosphere, the insulating layer, and the voltage relaxing layer, sothat even if the discharge starting voltage V in the atmosphere is setto be lower than conventionally, the relationship of the dischargestarting voltage V>the maximum applied voltage (BV) can be maintained.

Here, based on Paschen's Law, the discharge starting voltage V betweentwo electrodes is expressed by a function of the product of a gaspressure P and the interval between the electrodes (in the presentinvention, the distance X1 from the end of the pad area to the dicingregion) (V=f (P·X1)). According to the present invention, the dischargestarting voltage V in the atmosphere can be set to be lower thanconventionally, so that based on Paschen's Law, the distance X1 from theend of the pad area to the dicing region (end face of the SiC layer) canbe made shorter than conventionally.

Therefore, when the size of the semiconductor device (chip size) is setto be equal to the conventional one, the outer edge of the pad area canbe extended to the end face side of the SiC layer, so that the pad areaof the surface electrode can be made wider than conventionally. On theother hand, when the size of the pad area of the surface electrode isset to be equal to the conventional one, the end faces of the SiC layercan be shortened to the pad area side, so that the number ofsemiconductor devices (number of chips) to be obtained from one SiCwafer can be increased to be larger than conventionally.

Furthermore, even if a defect (such as a hole, etc., caused by a processfailure) occurs in one of the insulating layer and the voltage relaxinglayer, the defect can be covered by the other. Therefore, dischargebetween the dicing region and the surface electrode can be effectivelyprevented from occurring.

In the semiconductor device according to the present invention, it ispreferable that the maximum applied voltage (BV) Y (≥1000 V) of thesemiconductor device structure and the distance X1 from the end of thepad area to the end face of the SiC layer satisfy the followingrelational expression (1) (Claim 2). Regarding the manufacturing method,the step of forming the surface electrode preferably includes a step ofsetting the size of the pad area so that the maximum applied voltage(BV) Y (≥1000 V) of the semiconductor device structure and the distanceX1 from the end of the pad area to the dicing region satisfy thefollowing relational expression (1) (Claim 21).

$\begin{matrix}\lbrack {{Numerical}\mspace{14mu}{expression}\mspace{14mu} 1} \rbrack & \; \\{\mspace{146mu}{( {{855 \cdot \ln}\frac{Y}{1053}} ) \leqq {X\; 1} \leqq {( {{855 \cdot \ln}\frac{Y}{1053}} ) + 100}}} & (1)\end{matrix}$

As described above, by providing the insulating layer and the voltagerelaxing layer, in addition to the atmosphere and the firstconductive-type SiC, at least a plurality of layers are interposedbetween the dicing region and the surface electrode. The interpositionof these layers effectively prevents discharge between the dicing regionand the surface electrode.

On the other hand, between the surface electrode of one device regionand the surface electrode of a device region adjacent to the deviceregion mentioned above, pad areas individually exposed are linked toeach other via only the atmosphere. Therefore, when measuring theelectric characteristics of the semiconductor device structure, if themaximum applied voltage (BV) (≥1000 V) exceeds the discharge startingvoltage V in the atmosphere, discharge may occur between the surfaceelectrodes adjacent to each other.

According to the function V=f (P·X1) of Paschen's Law, as X1 decreases,the discharge starting voltage V also lowers. That is, as a result ofthe present invention, the distance X1 from the end of the pad area tothe dicing region (end face of the SiC layer) can be made shorter,however, according to this, the discharge starting voltage V between thesurface electrodes linked to each other via only the atmosphere alsolowers. Therefore, discharge between the surface electrodes is requiredto be prevented by preventing the maximum applied voltage (BV) fromexceeding the discharge starting voltage V in the atmosphere while thedistance X1 is kept as short as possible.

Therefore, in this arrangement, by satisfying the relational expression(1) described above, discharge between surface electrodes adjacent toeach other can be reliably prevented while the distance X1 from the endof the pad area to the dicing region (end face of the SiC layer) can bemade shorter than conventionally.

In the semiconductor device according to the present invention, it ispreferable that the distance X2 from the end of the connected portionconnected to the SiC layer of the surface electrode to the end face ofthe SiC layer is longer than the width of a depletion layer spreading inthe horizontal direction along the first surface of the SiC layer fromthe connected portion when the maximum applied voltage (BV) is appliedto the semiconductor device structure (Claim 3). Regarding themanufacturing method, the step of forming the surface electrodepreferably includes a step of setting a relative position of theconnected portion to the dicing region so that the distance X2 from theend of the connected portion connected to the SiC wafer of the surfaceelectrode to the dicing region becomes longer than the width of adepletion layer spreading in the horizontal direction along the firstsurface of the SiC wafer from the connected portion when the maximumapplied voltage (BV) is applied to the semiconductor device structure(Claim 22).

With this arrangement, in each of the semiconductor devices divided intoindividual pieces, the depletion layer spreading in the horizontaldirection from the connected portion connected to the SiC layer of thesurface electrode is prevented from reaching the end face of the SiClayer.

The semiconductor device according to the present invention preferablyfurther includes a second conductive-type termination structure formedto be annular along the periphery of the surface electrode in the SiClayer (Claim 4).

With this arrangement, the degree of extension of the depletion layerfrom the connected portion connected to the SiC layer of the surfaceelectrode can be adjusted. Furthermore, by adjusting the impurityconcentration of the termination structure, the maximum applied voltage(BV) of the semiconductor device structure can also be adjusted. In thiscase, a plurality of the termination structures may be formedconcentrically (Claim 5).

In the semiconductor device according to the present invention, theinsulating layer preferably has a structure consisting of a plurality oflayers including a first layer and a second layer laminated in orderfrom the SiC layer (Claim 6). With this arrangement, according to themagnitude of the maximum applied voltage (BV) required for thesemiconductor device structure, the kind of insulating layer can bevariously changed.

In the semiconductor device according to the present invention, it ispossible that the first layer is formed on the entire first surface ofthe SiC layer, the second layer has an outer peripheral edge retreatedto the inner side of the SiC layer with respect to the end faces of theSiC layer such that the first layer is partially exposed on the endportion of the the first surface of the SiC layer (Claim 7). In thiscase, the voltage relaxing layer may be formed to overlap the outerperipheral edge of the second layer in the thickness direction of theSiC layer (Claim 8), or may be formed so as not to overlap the outerperipheral edge of the second layer (Claim 9).

In the semiconductor device according to the present invention, thesecond layer preferably includes a convex portion that selectivelypenetrates the first layer and reaches the first surface of the SiClayer (Claim 10). In this case, a plurality of the convex portions ofthe second layer may be formed (Claim 11).

With this arrangement, even if the first layer peels from the end faceof the SiC layer, this peeling can be stopped by the convex portion ofthe second layer. Therefore, adhesiveness of the insulating layer to theSiC layer can be improved.

In the semiconductor device according to the present invention, both ofthe first layer and the second layer maybe formed on the entire firstsurface of the SiC layer (Claim 12).

In the semiconductor device according to the present invention, thefirst layer may be composed of any material of silicon oxide (SiO₂) witha thickness of 1 μm or more, polyimide with a thickness of 0.2 μm ormore, and silicon nitride (SiN) with a thickness of 1 μm or more (Claims13 to 15).

In the semiconductor device according to the present invention, theinsulating layer may have a structure consisting of a single layer(Claim 16).

In the semiconductor device according to the present invention, thesemiconductor device structure may include a Schottky barrier diodestructure formed by composing the surface electrode of a material thatforms a Schottky barrier between the surface electrode and the SiC layer(Claim 17). Furthermore, the semiconductor device structure may includean MIS transistor structure including second conductive-type channelregions selectively formed in the SiC layer, first conductive-typesource regions formed in contact with the channel regions, a gateinsulating film formed on the channel regions, and a gate electrodeopposed to the channel regions via the gate insulating film (Claim 18).

In the semiconductor device according to the present invention, the SiClayer may include an SiC substrate and an SiC epitaxial layer formed onthe SiC substrate, and the SiC epitaxial layer may have an impurityconcentration of 1×10¹⁶ cm⁻³ or less and a thickness of 5 μm or more.

Furthermore, in the method for manufacturing the semiconductor deviceaccording to the present invention, in the step of measuring a withstandvoltage of the semiconductor device structure, the measurement ispreferably performed at a pressure of 720 to 1520 Torr (Claim 23).

According to the function V=f (P·X1) of Paschen's Law, as the gaspressure P increases, the discharge starting voltage V also becomeshigher. Therefore, by setting the gas pressure P for measurement of theelectric characteristics in the above-described range, the distance X1from the end of the pad area to the dicing region (end face of the SiClayer) can be further shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a semiconductor device according to a firstpreferred embodiment of the present invention.

FIG. 2 is a sectional view taken along a cross-sectional line II-II inFIG. 1.

FIG. 3 is a flowchart for describing an example of a manufacturingprocess for manufacturing the semiconductor device.

FIG. 4 is a diagram for describing an effect relating to the distance X1from an end of a pad area to an end face of an SiC layer.

FIG. 5 is a diagram for describing an effect relating to the distance X2from an end of a connected portion connected to the SiC layer of theanode electrode to an end face.

FIG. 6 is a sectional view for describing an arrangement of asemiconductor device according to a second preferred embodiment of thepresent invention.

FIG. 7 is a sectional view for describing an arrangement of asemiconductor device according to a third preferred embodiment of thepresent invention.

FIG. 8 is a sectional view for describing an arrangement of asemiconductor device according to a fourth preferred embodiment of thepresent invention.

FIG. 9 is a sectional view for describing an arrangement of asemiconductor device according to a fifth preferred embodiment of thepresent invention.

FIG. 10 is a sectional view for describing an arrangement of asemiconductor device according to a sixth preferred embodiment of thepresent invention.

FIG. 11 is a sectional view for describing an arrangement of asemiconductor device according to a seventh preferred embodiment of thepresent invention.

FIG. 12 is a sectional view for describing an arrangement of asemiconductor device according to an eighth preferred embodiment of thepresent invention.

FIG. 13 is a sectional view for describing an arrangement of asemiconductor device according to a ninth preferred embodiment of thepresent invention.

FIG. 14 is a view for describing an example of a planar structure of thesemiconductor device shown in FIG. 13.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention aredescribed in detail with reference to the accompanying drawings.

FIG. 1 is a plan view of a semiconductor device according to a firstpreferred embodiment of the present invention. FIG. 2 is a sectionalview taken along a cross-sectional line II-II in FIG. 1. In FIG. 1 andFIG. 2, for easy understanding of the contents of the present invention,semiconductor devices before being divided into individual pieces from awafer are shown.

The semiconductor device 1 is a device using silicon carbide (SiC). Anumber of semiconductor devices 1 are regularly aligned and formed onone SiC wafer 2. On the SiC wafer 2 (hereinafter, also referred to as“SiC layer 2”), a dicing region 4 with a predetermined width a (forexample, 30 μm to 80 μm) that segments a plurality of device regions 3is set. In the present preferred embodiment, the dicing region 4 isformed in a grid manner, and the plurality of device regions 3 arealigned in matrix as a whole. The semiconductor device 1 is formed ineach device region 3, and the semiconductor devices are divided intoindividual pieces by cutting the SiC wafer 2 along the dicing region 4.The semiconductor device 1 according to the first preferred embodimentis a Schottky barrier diode.

The SiC layer 2 of each semiconductor device cut out by dividing intoindividual pieces has a first surface 2A and a second surface 2B, andend faces 2C surrounding the first surface 2A and the second surface 2B.The end faces 2C are SiC layer cutting surfaces (side surfaces)appearing by dividing into individual pieces, and segment the outerperipheries of the first surface 2A and the second surface 2B. In thepresent preferred embodiment, each semiconductor device 1 has a chipshape square in a plan view. As the size of the chip, the lengths in theup-down direction and the left-right direction of the sheet of FIG. 1are 0.5 mm to 20 mm. Specifically, the chip size of the semiconductordevice 1 is, for example, 0.5 mm square to 20 mm square.

The SiC layer 2 includes a substrate 5 composed of n⁺-type SiC and anepitaxial layer 6 composed of n⁻-type SiC formed on the substrate 5. Thethickness of the substrate 5 may be 50 μm to 1000 μm, and the thicknessof the epitaxial layer 6 may be 5 μm or more (preferably 6 μm to 20 μm).As an n-type dopant contained in the substrate 5 and the epitaxial layer6, for example, N (nitrogen), P (phosphorus), As (arsenic), etc., can beused (the same applies to the description given below). As arelationship between the dopant concentration of the substrate 5 and thedopant concentration of the epitaxial layer 6, the dopant concentrationof the substrate 5 is relatively high, and the dopant concentration ofthe epitaxial layer 6 is relatively lower than that of the substrate 5.In detail, the dopant concentration of the substrate 5 may be 1×10¹⁷ to1×10²² cm⁻³, and the dopant concentration of the epitaxial layer 6 maybe 1×10¹⁶ cm⁻³ or less (preferably 1×10¹⁵ to 9×10¹⁵ cm⁻³).

In the superficial portion of the epitaxial layer 6, a p-type voltagerelaxing layer 7 is formed to be exposed to the end portion of the firstsurface 2A. In the present preferred embodiment, the voltage relaxinglayer 7 is formed to be annular along the outer peripheral edge of theSiC layer 2 so as to be exposed to the corner portions on the firstsurface 2A side of the SiC layer 2 defined by the first surface 2A andthe end faces 2C of the SiC layer 2. Accordingly, the voltage relaxinglayer 7 is exposed to both of the first surface 2A and the end faces 2C,and the regions exposed to the faces 2A and 2C are integrated at thecorner portion of the SiC layer 2. As a p-type dopant contained in thevoltage relaxing layer 7, for example, B (boron), Al (aluminum), etc.,can be used. The voltage relaxing layer 7 is formed so that the bottomportion thereof is positioned on the first surface 2A side with respectto the boundary between the substrate 5 and the epitaxial layer 6. Indetail, the depth of the voltage relaxing layer 7 may be, for example,1000 to 10000 angstroms.

On the SiC layer 2, an insulating layer 8 and an anode electrode 9 as asurface electrode are formed. The insulating layer 8 is formed to coverthe voltage relaxing layer 7, and has a structure consisting of aplurality of layers including a first layer 81 and a second layer 82laminated in order from the SiC layer 2. When the insulating layer 8 hasa structure consisting of a plurality of layers, according to themagnitude of the maximum applied voltage (BV) required for the Schottkybarrier diode, the kind of insulating layer 8 can be variously changed.

In the present preferred embodiment, the first layer 81 is formed on theentire first surface 2A of the SiC layer 2. On the other hand, thesecond layer 82 is formed so as to expose the portions on the corners ofthe first surface 2A of the SiC layer 2 in the first layer 81, and hasan outer peripheral edge 83 retreated to the inner side of the SiC layer2 with respect to the end faces 2C. In detail, the voltage relaxinglayer 7 covered by the insulating layer 8 is formed to overlap the outerperipheral edge 83 of the second layer 82 in the thickness direction ofthe SiC layer 2. Specifically, the inner peripheral edge 71 of thevoltage relaxing layer 7 is positioned on the inner side of the SiClayer 2 as compared with the outer peripheral edge 83 of the secondlayer 82. In the first layer 81, a contact hole 84 that selectivelyexposes the first surface 2A of the SiC layer 2 is formed.

The anode electrode 9 includes a lower end portion 91 embedded in thecontact hole 84 and an upper end portion 92 protruding upward from thefirst layer 81, and the bottom surface of the lower end portion 91 isconnected as a connected portion 93 to the first surface 2A of the SiClayer 2 inside the contact hole 84. The upper end portion 92 of theanode electrode 9 further includes a drawn-out portion 94 as aperipheral edge portion uniformly drawn-out in the horizontal direction(direction along the first surface 2A of the SiC layer 2) from the outerperipheral edge of the contact hole 84. Accordingly, the anode electrode9 is formed to have a size larger than the opening diameter of thecontact hole 84 in a plan view.

The peripheral edge portion of the upper end portion 92 of the anodeelectrode 9 is covered by the second layer 82 higher than the anodeelectrode. That is, in the second layer 82, a contact hole 85 thatselectively exposes the central portion of the anode electrode 9 as apad area 95 is formed. The contact hole 85 is formed so that therelative position of the outer peripheral edge to the end faces 2C ofthe SiC layer 2 is further inside than the outer peripheral edge of thecontact hole 84. The detailed size of the contact hole 85 is, forexample, 500 μm×300 μm when a bonding wire with a 125 μm diameter isconnected to the pad area 95.

In the insulating layer 8, in the present preferred embodiment, thefirst layer 81 is composed of silicon oxide (SiO₂) with a thickness of 1μm or more, and the second layer 82 is composed of polyimide with athickness of 0.2 μm or more. However, the materials of the insulatinglayer 8 are not limited to these. For example, the first layer 81 may becomposed of polyimide with a thickness of 0.2 μm or more or siliconnitride (SiN) with a thickness of 1 μm or more. Among these materials,in terms of adhesiveness to the SiC layer 2, SiO₂ is most preferable.

The anode electrode 9 can be composed of a material that forms aSchottky barrier or hetero junction with respect to the n-type SiC layer2, specifically, Mo (molybdenum), Ti (titanium), Ni (nickel), or Al(aluminum) as an example of the former material, or polysilicon as anexample of the latter material, or the like. That is, the anodeelectrode 9 forming a Schottky barrier in this semiconductor device 1may be either of a metal electrode that forms a Schottky barrier betweenthe electrode and the SiC layer 2, and a semiconductor electrode that iscomposed of a semiconductor having a band gap different from that of theSiC layer 2, and makes a hetero junction to the SiC layer 2 (junctionforming a potential barrier between the electrode and the SiC layer 2 byutilizing a band gap difference).

In this semiconductor device 1, when it turns into a forward bias statewhere a positive voltage is applied to the anode electrode 9 and anegative voltage is applied to the cathode electrode (not illustrated),electrons (carriers) move from the cathode electrode to the anodeelectrode 9 through the SiC layer 9 and an electric current flows.Accordingly, the semiconductor device 1 (Schottky barrier diode)operates.

Next, a method for manufacturing the semiconductor device 1 is describedwith reference to FIG. 1 to FIG. 3. FIG. 3 is a flowchart for describingan example of a manufacturing process for manufacturing thesemiconductor device.

First, an SiC wafer 2 formed of the substrate 5 and the epitaxial layer6 is prepared. In this SiC wafer 2, as described above, device regions 3in which a plurality of semiconductor devices 1 are formed, and a dicingregion 4 that segments the device regions 3 and defines the end faces 2Cof the plurality of semiconductor devices 1 to be finally divided intoindividual pieces and separated from each other, are set in a gridmanner.

Next, for example, by selectively applying ion implantation andannealing to the first surface 2A of the SiC layer 2, the voltagerelaxing layer 7 is formed (Step S1). The voltage relaxing layer 7 isformed along the dicing region 4 so as to have a width β that is widerthan the width a of the dicing region 4 and across the device regions 3adjacent to each other in the middle of manufacturing. That is, in thepresent preferred embodiment, the voltage relaxing layer 7 is formed ina grid manner with a width β wider than the width a of the dicing region4 (refer to the alternate long and short dash line in FIG. 1).

Next, according to a known film formation method such as CVD, the firstlayer 81 is formed on the entire first surface 2A of the SiC layer 2(Step S2).

Next, the contact holes 84 that selectively expose the first surface 2Aof the SiC layer 2 are formed in the first layer 81, and then, forexample, by sputtering, the material of the anode electrodes 9 isdeposited and patterned to define the anode electrodes 9 (Step S3). Theanode electrodes 9 are connected to the SiC layer 2 (epitaxial layer 6)through the contact holes 84 of the first layer 81.

Next, by a known film formation method such as CVD, the second layer 82is formed on the first layer 81 so as to cover the entire anodeelectrodes 9 (Step S4). Next, by patterning the second layer 82, thecontact holes 85 that selectively expose the central portions of theanode electrodes 9 as pad areas 95 are formed (Step S5). Simultaneously,the grid-shaped portion along the dicing region 4 of the second layer 82is selectively removed, and the outer peripheral edge 83 of the secondlayer 82 is retreated to the inner side of each device region 3 withrespect to the lines being the end faces 2C. Through the above-describedsteps, in each device region 3, a Schottky barrier diode (semiconductordevice structure) is defined by junction between the SiC layer 2 and theanode electrode 9.

The next step is measurement of the electric characteristics of eachSchottky barrier diode (Step S6). In detail, the anode electrode 9 ofone device region 3 is set to 0 V, and the second surface of the SiCwafer 2 is set to 1000 V or more (for example, 1700 V). Accordingly, amaximum applied voltage (BV) that generates a potential difference of1000 V or more is applied between the anode electrode 9 and the SiCwafer 2, and a withstand voltage of each Schottky barrier diode ismeasured.

At this time, the n-type portion of the SiC wafer 2 including a part(except for the voltage relaxing layer 7) of the dicing region 4 isfixed to a potential of 1000 V or more, so that between the dicingregion 4 and the anode electrode 9, a potential difference of 1000 V ormore is generated. Even in this case, according to the present preferredembodiment, the voltage relaxing layer 7 is formed along the dicingregion 4, and the voltage relaxing layer 7 is further covered by theinsulating layer 8. Therefore, the maximum applied voltage (BV) of 1000V or more applied between the dicing region 4 and the anode electrode 9can be relaxed in two stages of the insulating layer 8 and the voltagerelaxing layer 7. Accordingly, the burden of the voltage on theatmosphere between the dicing region 4 and the anode electrode 9 can beeased. In other words, as shown in FIG. 2, the voltage applied betweenthe dicing region 4 and the anode electrode 9 can be divided by theatmosphere section 10, the insulating layer section 11, and the voltagerelaxing layer section 12. Therefore, even when the discharge startingvoltage V in the atmosphere section 10 is made lower thanconventionally, the relationship of the discharge starting voltage V>themaximum applied voltage (BV) can be maintained.

Here, based on Paschen's Law, the discharge starting voltage V betweentwo electrodes is expressed by a function of the product of a gaspressure P and the interval between the electrodes (in the presentpreferred embodiment, the distance X1 from the end of the pad area 95(outer peripheral edge of the contact hole 85) to the dicing region 4)(V=f (P·X1)). With this semiconductor device 1, the discharge startingvoltage V of the atmosphere section 10 can be made lower thanconventionally, so that according to Paschen's Law, the distance X1 canbe made shorter than conventionally.

Therefore, when the size of the semiconductor device 1 (chip size) ismade equal to the conventional one, the outer edge of the pad area 95can be widened to the end face 2C side of the SiC layer 2, so that thepad area 95 can be made wider than conventionally. On the other hand,when the size of the pad area 95 is made equal to the conventional size,the end faces 2C of the SiC layer 2 can be shortened to the pad area 95side, so that the number of semiconductor devices 1 (number of chips) tobe obtained from one SiC wafer 2 can be increased to be larger thanconventionally.

Furthermore, even if a defect (for example, a hole, etc., caused by aprocess failure) occurs in one of the insulating layer 8 and the voltagerelaxing layer 7, the defect can be covered by the other. Therefore,discharge between the dicing region 4 and the anode electrode 9 can beeffectively prevented from occurring.

Measurement of the electric characteristics of the Schottky barrierdiode can be performed in a gas atmosphere of, for example, theatmosphere, nitrogen (N₂), hydrogen (H₂), argon (Ar), neon (Ne), helium(He), or the like. The gas pressure P at this time is preferably, forexample, 720 Torr to 1520 Torr.

According to the function V=f (P·X1) of Paschen's Law, as the gaspressure P increases, the discharge starting voltage V also becomeshigher. Therefore, by setting the gas pressure P for measurement of theelectric characteristics in the above-described range, the distance X1from the end of the pad area 95 to the dicing region 4 (end face 2C ofthe SiC layer 2) can be further shortened.

Thereafter, the electric characteristics of the Schottky barrier diodesin all device regions 3 are measured according to the same method. Afterthe measurement, the SiC wafer 2 is cut into the individualsemiconductor devices 1 by cutting along the dicing region 4. Thus, thesemiconductor devices 1 having the structure shown in FIG. 2, etc., areobtained.

Next, effects relating to the distance X1 from the end of the pad area95 to the end face 2C of the SiC layer 2 are described with reference toFIG. 4.

In the semiconductor device 1, it is preferable that the maximum appliedvoltage (BV) Y (≥1000 V) to be applied to the Schottky barrier diode andthe distance X1 from the end of the pad area 95 to the end face 2C ofthe SiC layer 2 satisfy the following relational expression (1). In themanufacturing process, it is preferable that the size of the pad area 95(the size of the contact hole 85) is set so that the maximum appliedvoltage (BV) Y (≥1000 V) to be applied to the Schottky barrier diode andthe distance X1 from the end of the pad area 95 to the dicing region 4satisfy the following relational expression (1) when exposing the padarea 95 by patterning the second layer 82 (Step S5).

$\begin{matrix}\lbrack {{Numerical}\mspace{14mu}{expression}\mspace{14mu} 2} \rbrack & \; \\{\mspace{146mu}{( {{855 \cdot \ln}\frac{Y}{1053}} ) \leqq {X\; 1} \leqq {( {{855 \cdot \ln}\frac{Y}{1053}} ) + 100}}} & (1)\end{matrix}$

As described above, by providing the insulating layer 8 and the voltagerelaxing layer 7, in addition to the atmosphere section 10, theinsulating layer section 11 and the voltage relaxing layer section 12are interposed between the dicing region 4 and the anode electrode 9.The interposition of the insulating layer 8 and the voltage relaxinglayer 7 effectively prevents discharge between the dicing region 4 andthe anode electrode 9.

On the other hand, in the section (section 13) between the anodeelectrode 9 of one device region 3 and the anode electrode 9 of thedevice region 3 adjacent to the device region 3 mentioned above, padareas 95 individually exposed are linked to each other via only theatmosphere. Therefore, at the time of measurement of the electriccharacteristics of the Schottky barrier diode (Step S6), if the maximumapplied voltage (BV) (≥1000 V) exceeds the discharge starting voltage Vin the atmosphere, discharge may occur between the anode electrodes 9adjacent to each other.

According to the function V=f (P·X1) of Paschen's Law, as X1 decreases,the discharge starting voltage V also lowers. That is, as a result ofthe present invention, the distance X1 from the end of the pad area 95to the dicing region 4 (end face 2C of the SiC layer 2) can be madeshorter, however, according to this, the discharge starting voltage V inthe section 13 linked via only the atmosphere also lowers. Therefore,discharge in the section 13 must be prevented by preventing the maximumapplied voltage (BV) from exceeding the discharge starting voltage V inthe atmosphere while the distance X1 is kept as short as possible.

Therefore, in this semiconductor device 1, by satisfying theabove-described relational expression (1), discharge between anodeelectrodes 9 adjacent to each other can be reliably prevented while thedistance X1 from the end of the pad area 95 to the dicing region 4 (endface 2C of the SiC layer 2) can be made shorter than conventionally.

In detail, as a result of investigation performed by the inventor of thepresent invention, the relationship between the discharge startingvoltage V between two electrodes linked to each other via only theatmosphere and the discharge distance can be shown by the graph(Y=1.053E+03e^(5.846E−04X)) of FIG. 4(a). In this expression, “E” is anexponential expressed in decimal (the same applies to the descriptionhereinafter). For example, 1.053E+03 expresses 1.053×10³. e^(5.846E−04X)expresses exp(5.846×10⁻⁰⁴−X). Referring to FIG. 4(a), in the case wherethe discharge distance (distance between two electrodes) is 200 μm, 400μm, or 700 μm, discharge may occur when a potential difference of 1200 Vor more, 1300 V or more, or 1600 V or more occurs between the twoelectrodes. That is, in FIG. 4(a), discharge may occur in the case wherethe coordinates are included in the upper side region (shaded portion)of the graph.

The inventor of the present invention further examined the relationshipbetween the maximum applied voltage (BV) Y and the distance X1 in thesemiconductor device 1 based on FIG. 4(a). In the semiconductor device1, the distance corresponding to the discharge distance of FIG. 4(a) isthe shortest distance between anode electrodes 9 adjacent to each other.This shortest distance corresponds to 2 times (2 (X1)) the distance X1from the end of each pad area 95 (outer peripheral edge of the contacthole 85) to the dicing region 4 (to be exact, 2 (X1)+α, however, thewidth a is ignored here). Therefore, in the semiconductor device 1, inthe case where the distance X1=100 μm, 200 μm, or 350 μm, when apotential difference of 1200 V or more, 1300 V or more, or 1600 V ormore occurs between the anode electrodes 9 adjacent to each other at thetime of measurement of the electric characteristics of the Schottkybarrier diode, discharge may occur between these. That is, when themaximum applied voltage (BV) that generates this potential difference isapplied to the anode electrode 9 of one device region 3, discharge mayoccur between this anode electrode and the anode electrode 9 of thedevice region 3 adjacent to the device region 3 mentioned above.

The graph of FIG. 4(b) shows graphically the relationship between themaximum applied voltage (BV) Y and the distance X1 in the semiconductordevice 1 in consideration of the description given above. The graph ofFIG. 4(b) shows the function of Y=1.053E+03^(e1.16E−03X1). By convertingthis function into an expression for X1, X1=855·In (Y/1053) is obtained.In FIG. 4(b), discharge may occur when the coordinates are included inthe upper region (shaded portion) of the graph, and discharge isunlikely to occur when the coordinates are included in the lower region.Therefore, in order to reliably prevent discharge from occurring betweenanode electrodes 9 adjacent to each other, the coordinates of themaximum applied voltage (BV) Y and the distance X1 must be included inthe lower region of the graph.

However, even when the coordinates are included in the lower region, thedistance X1 is preferably as short as possible to obtain the effects ofwidening the pad area 95 and increasing the number of semiconductordevices 1 to be obtained.

Therefore, in the present preferred embodiment, as described above,setting is made so that the maximum applied voltage (BV) Y and thedistance X1 satisfy the following relational expression (1).

$\begin{matrix}\lbrack {{Numerical}\mspace{14mu}{expression}\mspace{14mu} 3} \rbrack & \; \\{\mspace{146mu}{( {{855 \cdot \ln}\frac{Y}{1053}} ) \leqq {X\; 1} \leqq {( {{855 \cdot \ln}\frac{Y}{1053}} ) + 100}}} & (1)\end{matrix}$

This relational expression (1) shows that the coordinates of the maximumapplied voltage (BV) Y and the distance X1 are included in the region(hatched portion) surrounded by X1=855·In (Y/1053) and X1=855·In(Y/1053)+100. Accordingly, while the distance X1 from the end of the padarea 95 to the dicing region 4 (end face 2C of the SiC layer 2) can bemade shorter than conventionally, discharge between the anode electrodes9 adjacent to each other can be reliably prevented.

Next, effects relating to the distance X2 from the end of the connectedportion 93 connected to the SiC layer 2 of the anode electrode 9 to theend face 2C are described.

In the semiconductor device 1, the distance X2 from the end of theconnected portion 93 (outer peripheral edge of the contact hole 84)connected to the SiC layer 2 of the anode electrode 9 to the end face 2Cis preferably longer than the width X3 of the depletion layer 14spreading in the horizontal direction along the first surface 2A of theSiC layer 2 from the connected portion 93 when the maximum appliedvoltage (BV) is applied to the Schottky barrier diode. In themanufacturing process, the contact hole 84 is formed in the first layer81, and when the anode electrode 9 is connected to the SiC layer 2through the contact hole 84 (Step S3), the relative position of theconnected portion 93 to the dicing region 4 is preferably set so thatthe distance X2 from the end of the connected portion 93 to the dicingregion 4 becomes longer than the width X3 of the depletion layer 14.

Generally, it is said that the depletion layer in the semiconductorlayer composed of SiC extends to two times in the orthogonal direction(horizontal direction) with respect to the thickness direction (verticaldirection) of the semiconductor layer. If the distance X2 is shorterthan the width X3 of the depletion layer 14 at the time of applicationof the maximum applied voltage (BV), when the maximum applied voltage(BV) is applied to each of the semiconductor devices 1 divided intoindividual pieces, the depletion layer 14 may extend to the end face 2Cof the SiC layer 2. Therefore, in this semiconductor device 1, bysetting distance X2>width X3, the depletion layer 14 can be preventedfrom reaching the end face 2C of the SiC layer 2.

In addition, in this semiconductor device 1, the outer peripheral edgeof the contact hole 85 which becomes the starting point of the distanceX1 is positioned on the inner side of the end faces 2C of the SiC layer2 as compared with the outer peripheral edge of the contact hole 84which becomes the starting point of the distance X2. Therefore, thedistance X1 and the distance X2 satisfy X1>X2. Accordingly, by makingthe setting so that the distance X2 satisfies the relational expression(1) described above, the depletion layer 14 can be prevented from beingexposed at the end face 2C, and simultaneously, discharge between theanode electrodes 9 adjacent to each other can be reliably prevented.

Here, an example of the distance X2 is described by using detailednumerical values. For example, when the impurity concentration of theepitaxial layer 6 is 7×10¹⁵cm⁻³ and the thickness thereof is 7 μm, themaximum applied voltage (BV) becomes 1450V, theoretically. In this case,theoretically, the depletion layer 14 extends by 15.2 μm in the verticaldirection of the epitaxial layer 6. Therefore, theoretically, the widthX3 in the horizontal direction of the depletion layer 14 becomes 30.4μm. The distance X2 is required to be longer than the width X3, so thatunder this condition, the distance becomes X2>30.4 μm.

On the other hand, when the maximum applied voltage (BV) is 1450 V, thedischarge distance in the atmosphere becomes 550 μm with reference toFIG. 4(a). To reliably prevent discharge between the anode electrodes 9adjacent to each other, the distance X2 is required to be longer than ½of this discharge distance, so that the distance becomes X2>275 μm.

That is, to prevent only exposure of the depletion layer 14 at the endface 2C, the distance becomes X2>30.4 μm, and to prevent dischargebetween the anode electrodes 9 adjacent to each other as well, thedistance X2>275 μm.

FIG. 6 to FIG. 14 are drawings for describing constitutions ofsemiconductor devices according to the second to eighth preferredembodiments of the present invention. In FIG. 6 to FIG. 14, portionscorresponding to each portion shown in FIG. 2 described above aredesignated by the same reference symbols.

In the semiconductor device 102 shown in FIG. 6 according to the secondpreferred embodiment, a termination structure 15 is further formed inthe SiC layer 2. The termination structure 15 is formed to be annularalong the periphery of the anode electrode 9, and is across the insideand the outside of the contact hole 84 of the first layer 81. By thistermination structure 15, the degree of spreading of the depletion layer14 (refer to FIG. 5) from the connected portion 93 of the anodeelectrode 9 can be adjusted. Furthermore, by adjusting the impurityconcentration of the termination structure 15, the maximum appliedvoltage (BV) of the Schottky barrier diode can also be adjusted.Furthermore, a plurality of termination structures maybe formedconcentrically as in the semiconductor device 103 (third preferredembodiment) shown in FIG. 7.

In the first preferred embodiment, the voltage relaxing layer 7 isformed to overlap the outer peripheral edge 83 of the second layer 82 inthe thickness direction of the SiC layer 2, however, the voltagerelaxing layer 7 may be formed so as not to overlap the outer peripheraledge 83 of the second layer 82 as in the semiconductor device 104(fourth preferred embodiment) shown in FIG. 8. Specifically, the innerperipheral edge 71 of the voltage relaxing layer 7 may be positioned onthe outer side of the SiC layer 2 as compared with the outer peripheraledge 83 of the second layer 82.

In the first preferred embodiment, only the first layer 81 is formed onthe entire first surface 2A of the SiC layer 2, however, both of thefirst layer 81 and the second layer 82 may be formed on the entire firstsurface 2A of the SiC layer 2 as in the semiconductor deice 105 (fifthpreferred embodiment) shown in FIG. 9.

In the semiconductor devices 106 and 107 shown in FIG. 10 and FIG. 11according to the sixth and seventh preferred embodiments, the secondlayer 82 has a convex portion 86 that selectively penetrates the firstlayer 81 and reaches the first surface 2A of the SiC layer 2. Only oneconvex portion 86 may be formed as shown in FIG. 10, or a plurality ofthe convex portions may be formed as shown in FIG. 11. With thisarrangement, even if the first layer 81 peels from the end face 2C ofthe SiC layer 2, this peeling can be stopped by the convex portion 86 ofthe second layer 82. Therefore, adhesiveness of the insulating layer 8to the SiC layer 2 can be improved.

In the first preferred embodiment, the insulating layer 8 has astructure composed of a plurality of layers including the first layer 81and the second layer 82, however, the insulating layer 8 may have astructure composed of a single layer as in the semiconductor device 108(eighth preferred embodiment) shown in FIG. 12.

In the first preferred embodiment described above, the semiconductordevice structure formed in the SiC layer 2 is a Schottky barrier diodestructure including the SiC layer 2 and the anode electrode 9 that formsa Schottky barrier between the anode electrode and the SiC layer 2,however, in the semiconductor device 109 shown in FIG. 13, an MIS (MetalInsulator Semiconductor) transistor structure is formed as asemiconductor device structure.

The MIS transistor structure includes the SiC layer 2, the p-typechannel regions 16, the n⁺-type source regions 17, the p⁺-type channelcontact regions 18, the gate insulating film 19, and the gate electrode20. The semiconductor device 109 further includes an interlayerinsulating film 21 and a source electrode 22 as a surface electrode ascomponents attached to the MIS transistor structure.

The channel regions 16 are selectively formed in the superficial portionof the epitaxial layer 6, for example, in a plurality of regionsdiscretely disposed periodically on the SiC layer 2. The channel regions16 may be disposed in, for example, a matrix, zigzag, or striped manner.

The source region 17 is formed in the inside region of the channelregion 16. In this region, the source region 17 is selectively formed inthe superficial portion of the channel region 16. The source region 17is formed inside the channel region 16 so as to be positioned at apredetermined distance inward from the interface between the channelregion 16 and the epitaxial layer 6. Accordingly, in the surface layerregion of the semiconductor layer including the epitaxial layer 6 andthe channel region 16, etc., between the source region 17 and theepitaxial layer 6, the superficial portion of the channel region 16 isinterposed, and this interposed superficial portion provides the channelportion 23.

The channel contact region 18 penetrates through the source region 17and is connected to the channel region 18.

The gate insulating film 19 may be composed of, for example, a siliconoxide film, a silicon nitride film, a silicon oxynitride film, a hafniumoxide film, an alumina film, a tantalum oxide film, or the like. Thegate insulating film 19 is formed to cover at least the surfaces of thechannel regions 16 in the channel portions 23.

The gate electrode 20 is formed such that it is opposed to the channelportions 23 via the gate insulating film 19. The gate electrode 20 maybe composed of polysilicon that is reduced in resistance by implantingimpurities. In the present preferred embodiment, the gate electrode 20is formed in almost the same pattern as that of the gate insulating film19, and covers the surfaces of the gate insulating film 19. Accordingly,a planar gate structure is arranged.

The interlayer insulating film 21 can be formed as, for example, anextended portion obtained by extending the first layer 81 along thefirst surface 2A of the SiC layer 2. The interlayer insulating film 21is formed in a pattern that covers the upper surfaces and side surfacesof the gate electrode 20 and has contact holes 24 in the central regionsof the channel regions 16 and the inner edge regions of the sourceregions 17 linked to the central regions.

The source electrode 22 is composed of aluminum (Al) and other metals.The source electrode 22 is formed to cover the surfaces of theinterlayer insulating film 21 and be embedded in the contact holes 24.Accordingly, the source electrode 22 forms an ohmic contact with thesource regions 17. Examples of a planar profile of the source electrode22 are shown in FIG. 14(a) to FIG. 14(c). In FIG. 14(a) to FIG. 14(c),the source electrode 22 is formed to cover almost the entire area of thesurface of the semiconductor device 109. In a part of the sourceelectrode 22, a removed region 25 is selectively formed. In the removedregion 25, a terminal to be electrically connected to the gate electrode20 is formed. In detail, in FIG. 14(a) and FIG. 14(b), gate pads 26 and27 are respectively formed, and in FIG. 14(c), gate fingers 28 areformed. A part of the source electrode 22 is exposed as a pad area 221from the contact hole 85 of the second layer 82 of the insulating layer8.

This semiconductor device 109 may include a p-type annular region 29surrounding the MIS transistor structure in the SiC layer 2, and acontact region 30 formed in the superficial portion of the annularregion 29. The annular region 29 and the contact region 30 may beexposed from the contact hole 84 of the first layer 81. That is, whenthe source electrode 22 as a surface electrode is connected at aplurality of points of the SiC layer 2, the outermost connected portion(in the present preferred embodiment, the connected portion 222connected to the contact region 30) corresponds to the “connectedportion connected to the SiC layer of the surface layer” of the presentinvention.

In this ninth preferred embodiment, a planar gate structure is describedas an example of the MIS transistor structure, however, the MIStransistor structure may be a trench-gate structure.

Preferred embodiments of the present invention are described above,however, the present invention may be carried out in other modes.

For example, an arrangement in which the conductive-types of eachsemiconductor portion of the semiconductor devices 1, 101 to 109 areinverted may be adopted. For example, in the semiconductor device 1, thep-type portion may be n-type, and the n-type portion may be p-type.

The voltage relaxing layer 7 must be a conductive-type (in the preferredembodiments described above, p-type) different from that of the SiClayer 2, however, in the inside region thereof, may have a portion theconductive-type of which is the same as that of the SiC layer 2. Forexample, the voltage relaxing layer 7 may have an n-type regionpositioned at a predetermined distance inward from the interface betweenthe voltage relaxing layer 7 and the epitaxial layer 6. As the n-typeregion is formed, for example, in the arrangement shown in FIG. 13,charge-up can be prevented when forming the n⁺-type source region 17 byion implantation.

The semiconductor device (semiconductor power device) according to thepresent invention can be installed in a power module that is used in aninverter circuit constituting a drive circuit for driving an electricmotor to be used as a power source of, for example, an electric vehicle(including a hybrid vehicle), train, an industrial robot, or the like.The semiconductor device can also be installed in a power module to beused in an inverter circuit that converts electric power generated by apower generator (in particular, private electric generator) such as asolar cell, a wind power generator, or the like, so as to match electricpower of a commercial power source.

The features understood from the disclosure of the above-describedpreferred embodiments may also be combined between different preferredembodiments. Furthermore, the components presented in the preferredembodiments may be combined within the scope of the present invention.

In addition, various design changes are possible within the scope of thematters described in the claims.

DESCRIPTION OF REFERENCE SIGNS

-   1: semiconductor device-   2: SiC wafer (SiC layer)-   2A: first surface-   2B: second surface-   2C: end face-   3: device region-   4: dicing region-   5: substrate-   6: epitaxial layer-   7: voltage relaxing layer-   8: insulating layer-   81: first layer-   82: second layer-   83: outer peripheral edge-   86: convex portion-   9: anode electrode-   93: connected portion-   95: pad area-   14: depletion layer-   15: termination structure-   16: channel region-   17: source region-   19: gate insulating film-   20: gate electrode-   22: source electrode-   221 pad area-   222 connected portion-   102 semiconductor device-   103 semiconductor device-   104 semiconductor device-   105 semiconductor device-   106 semiconductor device-   107 semiconductor device-   108 semiconductor device-   109 semiconductor device

1-23. (canceled)
 24. A semiconductor device comprising: a firstconductive-type semiconductor layer having a front surface, a backsurface and end surfaces surrounding the front surface and the backsurface, the semiconductor layer having a semiconductor elementstructure at a side of the front surface; a surface electrode connectedto an electrode of the semiconductor element structure; an insulatinglayer formed on the front surface, a part of the surface electrodeexposed from the insulating layer as a pad area, wherein a maximumapplied voltage (BV) Y (≥1000 V) of the semiconductor element structureand a distance X1 from an end of the pad area to the end surface of thesemiconductor layer satisfy the following relational expression (1):$\begin{matrix}\lbrack {{Numerical}\mspace{14mu}{expression}\mspace{14mu} 1} \rbrack & \; \\{\mspace{146mu}{( {{855 \cdot \ln}\frac{Y}{1053}} ) \leqq {X\; 1} \leqq {( {{855 \cdot \ln}\frac{Y}{1053}} ) + 100}}} & (1)\end{matrix}$
 25. The semiconductor device according to claim 24,wherein the semiconductor layer includes an SiC layer.
 26. Thesemiconductor device according to claim 24, wherein the insulating layerhas a peripheral portion which is located inside with respect to the endsurface of the semiconductor layer.
 27. The semiconductor deviceaccording to claim 24, wherein the insulating layer includes a firstinsulating layer formed on the semiconductor layer side with respect tothe surface electrode.
 28. The semiconductor device according to claim27, wherein the insulating layer includes a second insulating layercovering a part of a front surface of the surface electrode.
 29. Thesemiconductor device according to claim 24, wherein the insulating layerincludes a first insulating layer and a second insulating layer, thesecond insulating layer has a peripheral portion which is located insidewith respect to the end surface of the semiconductor layer, and thefirst insulating layer has an exposed portion which is exposed upwardlyin a vertical direction with respect to the front surface of thesemiconductor layer.
 30. The semiconductor device according to claim 24,further comprising a second conductive-type termination structure formedto be annular along a periphery of the surface electrode in thesemiconductor layer.
 31. The semiconductor device according to claim 30,wherein a plurality of the termination structures are formedconcentrically.
 32. The semiconductor device according to claim 28,further comprising a second conductive-type voltage relaxing layerformed in the semiconductor layer such that the voltage relaxing layeris exposed to an end portion of the front surface of the semiconductorlayer, wherein the voltage relaxing layer is formed to overlap an outerperipheral edge of the second insulating layer in a thickness directionof the semiconductor layer.
 33. The semiconductor device according toclaim 28, further comprising a second conductive-type voltage relaxinglayer formed in the semiconductor layer such that the voltage relaxinglayer is exposed to an end portion of the front surface of thesemiconductor layer, wherein the voltage relaxing layer is formed so asnot to overlap an outer peripheral edge of the second insulating layerin a thickness direction of the semiconductor layer.
 34. Thesemiconductor device according to claim 28, wherein the secondinsulating layer includes a convex portion that selectively penetratesthe first insulating layer and reaches the front surface of thesemiconductor layer.
 35. The semiconductor device according to claim 34,wherein a plurality of the convex portions of the second insulatinglayer are formed.
 36. The semiconductor device according to claim 27,wherein the first insulating layer is composed of silicon oxide (SiO2)with a thickness of 1 μm or more.
 37. The semiconductor device accordingto claim 28, wherein the second insulating layer is composed ofpolyimide with a thickness of 0.2 μm or more.
 38. The semiconductordevice according to claim 27, wherein the first insulating layer iscomposed of silicon nitride (SiN) with a thickness of 1 μm or more. 39.The semiconductor device according to claim 24, wherein thesemiconductor element structure includes a Schottky barrier diodestructure formed by composing the surface electrode of a material thatforms a Schottky barrier between the surface electrode and thesemiconductor layer.
 40. The semiconductor device according to claim 24,wherein the semiconductor element structure includes MIS transistorstructure, and the MIS transistor structure includes a secondconductive-type channel region selectively formed in the semiconductorlayer, a first conductive-type source region formed in contact with thechannel region, a gate insulating film formed on the channel region, anda gate electrode opposed to the channel region via the gate insulatingfilm.
 41. The semiconductor device according to claim 24, wherein thesemiconductor layer includes a semiconductor substrate and asemiconductor epitaxial layer formed on the semiconductor substrate, andthe semiconductor epitaxial layer has an impurity concentration of1×10¹⁶ cm⁻³ or less and a thickness of 5 μm or more.
 42. Thesemiconductor device according to claim 28, wherein an end portion ofthe first insulating layer is flush with an end portion of the secondinsulating layer.
 43. The semiconductor device according to claim 40,further comprising a pad formed inside a region of the surface electrodein a plan view, the pad electrically connected to the source region.